Double-Network Bilayer Hydrogel Loaded with Puerarin and Curcumin for Osteochondral Repair

Osteochondral injuries, which could result in cartilage defects and damage to the subchondral bone, pose a significant challenge in the design of scaffolds for bone repair due to the different characteristics of bone and cartilage. In this study, we developed a double-network bilayer hydrogel scaffold composed of an upper layer and a lower layer reinforced with a ZnO nanoparticle. The double-network hydrogel consisted of carboxymethyl chitosan (CMCS), oxidized sodium alginate (OSA), and poly-(vinyl alcohol) (PVA) networks. The upper and lower layers were, respectively, loaded with puerarin (Pue) and curcumin (Cur) to facilitate simultaneous repair of cartilage and bone. The scaffold exhibited better water absorption, mechanical properties (tensile strength: 0.8 MPa), self-healing capacity (healing efficiency ≥ 90%), and adhesion (adhesive stress: 0.1 MPa). Approximately 70% of Pue was rapidly released within the first 5 days, while Cur, encapsulated in ZnO, exhibited sustained release over a period of 20 d. <i>In vitro</i> cell experiments revealed that soluble extracts from the scaffolds were noncytotoxic and promoted elevated alkaline phosphatase (ALP) expression and calcium deposition in MC3T3-E1 subclone 14 (MC3T3-14) cells, thereby enhancing bone repair. Meanwhile, extracts fostered the proliferation of ATDC5 cells and glycosaminoglycan (GAG) production, contributing to cartilage repair. In conclusion, the bilayer hydrogel has good properties and is beneficial for the proliferation and differentiation of osteoblasts and chondrocytes.